The subject matter herein relates generally to power combiners that combine radio frequency (RF) power from multiple sources to a common load or to power dividers that split the RF power from a common source to multiple loads.
High-power RF systems that operate at a designated frequency or within a frequency range are used within various technological fields, such as communication, industrial processing, medical imaging, and physics-related research. For example, particle accelerators may be used to generate isotopes. Particle accelerators, such as cyclotrons, include high-power RF generators that create electrical fields for accelerating particles. Static magnetic fields are provided by electromagnets and a magnet yoke that surrounds the acceleration chamber. The electrical fields are generated by a pair of RF dees that are located within the acceleration chamber. To operate the RF dees within the acceleration chamber, a considerable amount of RF power (e.g., 5 kilowatts to 2 megawatts) is generated by the RF power generator and delivered to the RF dees. The RF power generator may include, for example, oscillators, amplifiers, control circuitry, etc.
For applications that use a large amount of RF power, it may not be possible to receive the RF power from a single power source. In such instances, a power combiner combines the RF power from multiple RF power sources and then provides the RF power to the system (e.g., particle accelerator, heater, etc.). RF power combining can be a complex process that addresses various challenges, including impedance transformation and matching, losses, bandwidth, and power limitations. Size of the RF power combiner is another challenge, especially for applications in which the frequency range is less than 300 megahertz (MHz). The size of the RF power combiner is proportional to the wavelength, and the wavelength for 300 MHz or less is relatively large (e.g., one meter or more).
Several techniques for RF power combination are known, but each technique has one or more drawbacks. One technique that may be used to reduce the size of the RF power combiner uses coaxial cables that are wound about in compact space. However, it can be difficult to combine several RF power combiner units in one stage, thereby necessitating several power-combining stages. Each stage adds complexity, size, and additional RF losses to the overall system.
Power vacuum tubes are used for some high-power RF applications, particularly those applications that operate in the lower RF frequency bands. Power vacuum tubes, such as triodes and tetrodes, can be expensive. Although solid-state designs may be theoretically possible for lower RF frequency bands, power vacuum tubes are more cost-effective. For instance, power vacuum tubes are currently more capable of withstanding short-term overload conditions (e.g. output overvoltage, input overdrive, or mismatch load conditions). To address these overload conditions, a solid-state design may use protection circuitry. For example, a solid-state amplifier system that includes transistors may use circulators that direct reflected power to dummy loads to protect the transistors. Circulators can be expensive and also add complexity and size to the overall system. Other active feedback protection systems can be used, but they can also add complexity and size to the overall system.
Although the above discussion relates to power combiners, power dividers may have a similar structure for dividing or splitting the RF power. As such, power dividers may have similar challenges, such as those described above.